List:Internals« Previous MessageNext Message »
From:Øystein Grøvlen Date:February 12 2013 2:11pm
Subject:Re: debugging how query plans are made
View as plain text  
On 02/12/13 02:54 PM, Zardosht Kasheff wrote:
> Hello all,
> In MySQL and/or MariaDB, are there any hooks or methods one can use to
> learn why a query plan is chosen over alternatives? We sometimes
> notice that a different query plan is chosen for us than InnoDB (which
> may be fine, given we are a different storage engine), and we would
> like to better understand why. Is there any debug parameter that gets
> MySQL to output decisions made in the optimizer?

MySQL 5.6 has optimizer tracing which outputs the decisions made by the 
optimizer.  See

Hope this helps,

debugging how query plans are madeZardosht Kasheff12 Feb
  • Re: debugging how query plans are madeØystein Grøvlen12 Feb